Surface-hardened titanium or zirconium and their alloys and method of processing same

ABSTRACT

Surface-hardened pure titanium or pure zirconium, titanium-base alloys, or zirconium-base alloys having an aged coating of a metastable beta alloy layer of a titanium or zirconium-base metal applied thereon. A method of hardening the surface of pure titanium, pure zirconium, titanium-base alloys, or zirconium-base alloys, which includes coating a metastable beta alloy of a titanium-base or zirconium-base metal thereon, and aging said coated alloy at temperatures of 200*-600*C.

United States Patent 1 1 Ohtani et al.

[ SURFACE-HARDENED TITANIUM OR ZIRCONIUM AND THEIR ALLOYS AND METHOD OFPROCESSING SAME [75] Inventors: Shitoshi-Ohtani, Suita; MinoruNishigaki, Akashi, both of Japan [73] Assignee: Kobe Steel, Ltd.,Fukiai-ku, Kobe,

Japan 221 Filed: Mar. 22, 1971- [21 Appl. No.: 126,630

[52] U.S. Cl 148/133, 29/198, 148/32.5, 148/34, 148/127 [51] Int. Cl.C22f l/l8, B32b 15/00 [58] Field of Search 148/31.5, 32.5, 34, 133,

[56] References Cited V UNITED STATES PATENTS 3,645,803 2/1972 Huber etal 148/127 X 3,560,274 2/1971 Ogden....., 29/198 2,940,163 6/1960 Davies29/198 X 3,493,353 2/1970 Bergmann et al 29/l98 X .1 3,802,939 I Apr. 9,1974 2,932,887 4/1960 McCuaiget a1. 29/198 X OTHER, PUBLICATIONSMetallurgio, December 1957, pages 277-282 Metal Selector,- 1963 EditionReprinted from Oct. 14, 1963 Steel, page S40 Primary E.\'aminerCharlesN. Lovell Attorney, Agent, or Firm-Oblon, Fisher, Spivak, Mc- Clelland &Maier 57 ABSTRACT Surface-hardened pure titanium or pure zirconium,

titanium-base alloys, or zirconium-base alloys having thereon, and agingsaid coated alloyat temperatures of-200-600C. Y 12 Claims, 2 DrawingFigures HARDNESS (Hv) ATENTEBAPR 9 974 AFTER E 8 Lu 5 5 I L 6 i 2 J BASEMETAL DEPOSIT w o 600- E a AFTER AGING 50c 40W AFTER SOLUTION TREATMENT2 IOO- INVENTORS SHITOSHI OHTANI MINORU NISHIGAKI I ("Q") 6 fl 2 J @rg g.;'$,/o%

BASE METAL DEPOSIT SURFACE ATTORNEYS 1 SURFACE-HARDENED TITANIUM ORZIRCONIUM AND THEIR ALLOYS AND METHOD OF PROCESSING SAME BACKGROUND OFTHE INVENTION 1. Field Of Invention This invention relates tosurface-hardened titanium, zirconium or their alloys and to a method ofpreparing same. Moreparticularly, this invention relates tosurface-hardened, pure'titanium, pure zirconium, titanium-base alloys,or zirconium-base alloys, and to a method of surface-hardening suchmetals.

2. Description Of The Prior Art Generally, titanium and zirconium havesuperior corrosion resistance in comparison with the other metals,

and accordingly they are broadly used in the chemical 800C. to form asolid solution of nitrides and a diffusion layer. Usually, the titaniumor zirconium is contact-treated with a nitriding gas at temperatures offrom 8009 OOC. so as to harden their surfaces. Although this method hasbeen commercially applied, since the surface-hardened layer obtained isextremely thin, its 4 endurance period is very short, in spite of thevery complicated treating operation. Other priorart methods also havesimilar disadvantages, and hence are similarly ineffective for manycommercial applications.

SUMMARY OF THE INVENTION Accordingly, one object'of the presentinvention is to eliminate the aforementioned disadvantages ofconventional methods and to provide a novel and improved Briefly, theseand other objects are attained in one aspect of the present inventionwherein surfacehardened pure titanium or zirconium is provided by aprocess which comprises coating a metastable beta alloy layer of atitanium or zirconium-base metal onto said pure metal, and agingsaidcoating to give a hardness of at least 400 Vickers hardness or above.The

' aforementioned metastable beta alloys may be any of the Ti(Zr)-Motype, Ti(Zr)-V type, Ti(Zr)-Fe type, Ti(Zr)-Cr type, Ti(Zr)-Mn type,Ti(Zr)-Nb type, Ti(Zr)-Ta, and multi-element type alloys containingthree or more elements of the aforesaid two-element type alloys.

According to another aspect of the present invention,

surface-hardened titanium-base or zirconium-base alloys are provided bya process which comprises coating a metastable beta alloy' layer of atitanium or zirconium-base metal onto said alloy and aging as above. The

aforesaid titanium-base alloys may be of a Ti-6Al-4V type,Ti-5Al-2Cr-lFe type, Ti-5Al-2.5Sn type, Ti-

0.2Pd type, Ti-8Mn type, Ti-8Al-lMo-lV type, Ti6Al- 6V-2 Sntype,-Ti-4Al-3Mo-1V type, Ti-2Cu type, Ti- 2Al-2Mn type,Ti-2.25Al-llSn-5Zr-l-Mo-O.1Si type, Ti-5Al-5Sn-5Zr type, and the like.

The'aforesaid zirconium-base alloys may be Zircaloy' 2', Zircaloy-4, andthe like.

According to afurth er aspect of this invention, there is provided amethod of hardening the surface of pure titanium, pure zirconium, ortitanium-base or zirconium-base alloys, which comprises the steps ofcoating a metastable beta alloy of a titanium-base or zirconiumbasemetal thereon and aging said coated alloy at temperatures of 200-600C.Thus, a surface-hardened layer may be very effectively formed on thesurface of the metal to be treated according to this invention, invarious thickness suitable for the intended purpose.

In the method of this invention, if the metastable beta alloy of thetitanium-base or zirconium-base metalis aged at low temperatures of200600C., the beta phase is decomposed to precipitate the alpha phase orits intermediate phase, i.e., omega phase, and the alloy is extremelyhardened. This fact is utilized in this invention in such a manner thatthe metastable beta phase alloy of this type is coated in advance on thesurface of the metal to be treated, and then the coated surface is agedat a low temperature region so as to harden only the surface layer,providing a titanium or zirconium product.

The coating of the metastable .beta phase alloy may be provided on thesurface of the metal to be treated, for example, by diffusion welding orexplosive pressure welding. The most effective and simplest method,however, will often be deposit welding. In this case, since themetastable beta phase alloy to be deposited on the metal surface to betreated is common to the metal to be treated in the base metal, thewelded portion will have no possibility of becoming fragile bymetallurgical reaction.

In the method of this invention, the coated surface is aged in thetemperature range of 200-600C. for a suitable period of time in therange of 5 minutes to 20 BRIEF DESCRIPTION OF THE DRAWINGS A morecomplete appreciation of the invention will be readily obtained as thesame becomes better understood by reference to the following detaileddescription when taken in conjunction with the accompanying drawings,wherein:

FIGS. 1 and 2 are graphical representations of the hardness distributionobtained from a titanium-base alloy treated in accordance withthe'present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made toFIG. 1, which shows the hardness distribution obtained by the method ofthis invention. Pure titanium plate was prepared as the base metal to betreated. Ti- 1 5Mo-5Zr type alloy was deposited by TIG welding on thesurface of the pure titanium plate, which was then held in agingtreatment for six hours at 450C. Thus, as shown in FIG. 1, asurfacehardened layer having sufficiently high hardness could beobtained.

Referring now to FIG. 2, which also shows the hardness distributionobtained by the method of this invention, a titanium-base alloy plate ofthe Ti-5Al-2Cr-1Fe type was prepared as the'base metal to be treated.This alloy was also deposited in a manner similar to the methoddescribed above with reference to FIG. 1. The deposited alloy was thensubjected to solution treatment at a temperature of 800C. for 2 hours,cooled by water, age treated at a temperature of 450C. for 6 hours, andfinally cooled by air. Thus, as shown in FIG. 2, a surface-hardenedlayer having sufficiently high hardness could also be obtained.

It will be understood from the foregoing description that thesurface-hardened pure titanium, pure zirconium, or titanium-base orzirconium-base alloys of this invention have a coating of a metastablebeta alloy layer of a titanium or zirconium-base metal which has beenaged to a sufficienthardness. The thickness of the surface-hardenedlayer may be selected in accordance with the intended use. Furthermore,since this layer before the aging treatment is relatively soft, as seenfrom the graphs shown in the drawings, it is possible to easily work themetai, such as by cutting it or the like, even after the metal iscoated, and thereafter age the coating to form the hardened surface.Thus, the method of this invention is particularly adapted for producingagitator blades, valves, bushings, etc.

It should also be understood that since the method of this inventionforms an aged coating of a metastable beta phase alloy of the same typeof metal as that to be treated, the thickness of the surface-hardenedlayer may be suitably selected to suit the desired product. It is alsopossible to work the metal to any shape, due to the aforementionedeffects.

It will be appreciated that, while the foregoing disclosure relates onlyto preferred embodiments of the invention for preparing surface-hardenedpure titanium or zirconium, or titanium-base or zirconium-base alloys,numerous modifications or alterations will be apparent to those skilledin the art without departing from the spirit and scopeof the inventionas set forth in the appended .claims.

What is claimed as new and intended to be secured by letters patent ofthe United States is:

l. A titanium or titanium base alloy having a deposited Ti metastablebeta alloy layer thereon, said deposited layer being in an age hardenedcondition and having a hardness of at least 400 Vickers wherein saidtitanium base alloy is selected from the group consistingof T i-6Al-4V,Ti-SAl-ZCr-lFe, Ti-5Al-2.5Sn, Ti-0.2Pd, Ti-BMn, Ti-8Al-Mo-1V,Ti-6Al-6V-2Sn, Ti-4AI'73MO- 1V, Ti-2Cu, Ti-2Al-2Mn,Ti-2.25Al-l1Sn-5Zr-lMohaving a hardness ofatleast 400 Vickers, whereinsaid zirconium base alloy is selected from the group consisting ofzircaloy-Z and zircaloy-4 and wherein said metastable beta alloy isselected from the group consisting of Zr-Mo, Zr-V, Zr-Fe, Zr-Cr, Zr-Mn,Zr-Nb and Zr- Ta, and alloys containing three or more elements of theaforesaid two element alloys.

3. The titanium or titanium base alloy of claim 1, wherein said agehardening was conducted at a temperature of from 200 600C.

4. The zirconium or zirconium base alloy of claim 2, wherein said agehardening was conducted at a temperature of from 200 600C.

5. A method of hardening the surface of a titanium or titanium basealloy which comprises depositing a layer of a Ti metastable beta alloyonto the surface of said titanium or titanium base alloy, solution heattreating, quenching, and aging said alloy layer at temperatures of 200600C. for a period of 5 minutes to 20 hours to a Vickers hardness of atleast 400, wherein said titanium base alloy is selected from the groupconsisting of Ti-6Al-4V, Ti-5Al-2Cr-1Fe, Ti-5Al-2.5Sn, Ti-0.2Pd, Ti-8Mn,Ti-8Al-Mo-IV, Ti-6Al-6V-2Sn, Ti- 4Al-3Mo-1V, Ti-ZCu, Ti-2Al-2Mn,Ti-2.25Al-l lSn- 5Zr-lMo-0.1Si, and Ti-5Al-5Sn-5Zr and wherein saidmetastable beta alloy is selected from the group consisting of Ti-Mo,Ti-V, Ti-Fe, Ti-Cr, Ti-Mn, Ti-Nb, Ti-Ta and alloys containing three ormore elements of the aforesaid two element alloys.

6. A method of hardening the surface of a zirconium or zirconium basealloy which comprises:

depositing'a layer of a Zr metastable beta alloy onto the surface ofsaid zirconium or zirconium base alloy, solution heat treating,quenching, and aging said alloy at temperatures of 200 600C. for aperiod of 5 minutes to 20 hours to a Vickers hardness of at least 400,wherein said zirconium base alloy is selected from the group consistingof zircaloy-2 and zircaloy-4 and wherein said metastable beta alloy isselected from the group consisting of Zr- Mo, Zr-V, Zr-Fe, Zr-Cr, Zr-Mn,Zr-Nb and Zr-Ta, and alloys containing three or more elements of theaforesaid two element alloys.

7. The method of claim 6, wherein said metastable beta alloy is formedby diffusion welding.

'8. The method of claim 6, wherein said metastable beta alloy is formedby explosive pressure welding.

9. The method of claim 6, wherein said metastable beta alloy is fonnedby deposit welding.

10. The method of claim 5, wherein said metastable beta alloy is coatedby diffusion welding.

11. The method of claim 5, wherein said metastable beta alloy is formingby explosive pressure welding.

12. The method of claim 5, wherein said metastable beta alloy is formingby deposit welding.

2. A zirconium or zirconium base alloy having a deposited Zr metastablebeta alloy layer thereon, said deposited layer being in an age hardenedcondiTion and having a hardness of at least 400 Vickers, wherein saidzirconium base alloy is selected from the group consisting of zircaloy-2and zircaloy-4 and wherein said metastable beta alloy is selected fromthe group consisting of Zr-Mo, Zr-V, Zr-Fe, Zr-Cr, Zr-Mn, Zr-Nb andZr-Ta, and alloys containing three or more elements of the aforesaid twoelement alloys.
 3. The titanium or titanium base alloy of claim 1,wherein said age hardening was conducted at a temperature of from 200*-600*C.
 4. The zirconium or zirconium base alloy of claim 2, whereinsaid age hardening was conducted at a temperature of from 200* -600*C.5. A method of hardening the surface of a titanium or titanium basealloy which comprises depositing a layer of a Ti metastable beta alloyonto the surface of said titanium or titanium base alloy, solution heattreating, quenching, and aging said alloy layer at temperatures of200* - 600*C. for a period of 5 minutes to 20 hours to a Vickershardness of at least 400, wherein said titanium base alloy is selectedfrom the group consisting of Ti-6Al-4V, Ti-5Al-2Cr-1Fe, Ti-5Al-2.5Sn,Ti-0.2Pd, Ti-8Mn, Ti-8Al-Mo-1V, Ti-6Al-6V-2Sn, Ti-4Al-3Mo-1V, Ti-2Cu,Ti-2Al-2Mn, Ti-2.25Al-11Sn-5Zr-1Mo-0.1Si, and Ti-5Al-5Sn-5Zr and whereinsaid metastable beta alloy is selected from the group consisting ofTi-Mo, Ti-V, Ti-Fe, Ti-Cr, Ti-Mn, Ti-Nb, Ti-Ta and alloys containingthree or more elements of the aforesaid two element alloys.
 6. A methodof hardening the surface of a zirconium or zirconium base alloy whichcomprises: depositing a layer of a Zr metastable beta alloy onto thesurface of said zirconium or zirconium base alloy, solution heattreating, quenching, and aging said alloy at temperatures of 200* -600*C. for a period of 5 minutes to 20 hours to a Vickers hardness of atleast 400, wherein said zirconium base alloy is selected from the groupconsisting of zircaloy-2 and zircaloy-4 and wherein said metastable betaalloy is selected from the group consisting of Zr-Mo, Zr-V, Zr-Fe,Zr-Cr, Zr-Mn, Zr-Nb and Zr-Ta, and alloys containing three or moreelements of the aforesaid two element alloys.
 7. The method of claim 6,wherein said metastable beta alloy is formed by diffusion welding. 8.The method of claim 6, wherein said metastable beta alloy is formed byexplosive pressure welding.
 9. The method of claim 6, wherein saidmetastable beta alloy is formed by deposit welding.
 10. The method ofclaim 5, wherein said metastable beta alloy is coated by diffusionwelding.
 11. The method of claim 5, wherein said metastable beta alloyis forming by explosive pressure welding.
 12. The method of claim 5,wherein said metastable beta alloy is forming by deposit welding.